In a known slip control device, a device that restricts torque sent from a motor to the driving wheel when the driving wheel revolves without making contact by means of a torque output from the motor has been proposed in Japanese Patent Provisional Publication No. 2004-96825. Accordingly, a slip control technique for restricting motor torque by referring to a map showing a relation such that the torque upper limit value decreases as the angular acceleration increases when the driving wheel revolves without making contact has been known.
In that slip control technique, the angular acceleration driving wheel is decreased by determining the torque upper limit value in advance in accordance with the angular acceleration of the driving wheel. Since the torque that can be transmitted to the road surface by the driving wheel is not considered, the maximum value of torque that can be transmitted to the road surface by the driving wheel cannot be made the torque upper limit value.
Therefore, when the vehicle is accelerated again after the slip has been caused to converge, another slip occurs. Alternatively, it is sometimes difficult to rapidly cause the slip to converge.